Fuel agitator for stoker hoppers



Sept. 24, 1957 BEDARD FUEL AGITATOR FoR sT0xER HOPPERS' Filed sept. 14.1953 'Lionel Bealfd I nited States Patent Oflce 2,807,394 Patented Sept.24, 1957- FUEL AGITATOR FOR STOKER HOPPERS Lionel Bedard, Longueuil,Quebec, Canada Application september 14, 1953, serial No. 379,807

13 Claims. (Cl. 222-243) This invention relates to improvements inagitators for the contents of hoppers, such as those of mechanicalstokers, and the primary object of the invention is to provide means forbreaking up agglomerations of eomminuted material in a hopper and forensuring a uniform discharge from the hopper. A further object is' toprovide means for so controlling downward movement of material in ahopper as to prevent jamming of a material feeding element at the hopperoutlet during its feeding movement; and as to ensure the feeding of afull charge of material to said element during its charge receivingmovement. A still further Iobject is to provide an agitator soconstructed and arranged that it will require only a small amount ofpower for its operation. Another object isto provide simple, durable andinexpensive means as aforesaid which may be installed in existinghoppers quite as well as in new construction. Vari-ous other objects andthe advantages of the invention may be ascertained from the followingdescription and the accompany drawings.

To facilitate explanation, the invention will be hereafter :described inits application to a mechanical Stoker. In the operation of mechanicalstokers in which fuel drops through a chute into a downwardly taperinghopper, considerable difficulty is occasioned by the packing or wedgingof the fuel in the hopper, due to the momentum of the falling fuel andto the tapering of the passage through the hopper, which results in anirregular discharge from the hopper and Sometimes complete stopping ofvthe discharge. This is particularly the case if wet or sticky fuel ofsmall particle size is being fed. Further di'iculty is encountered attimes because lof the presence of strongly coherent masses of fuel or ofagglomerations thereof, suc-h as result from freezing of wet or stickyfuel, which masses are too large to pass down to the hopper outlet andsubstantially or completely stop the discharge of fuel from the hopper.Such fuel masses, even if small enough to pass the hopper outlet, arefrequently too large to fall free of ythe hopper and are caught betweenthe rear edge of the hopper mouth and the rearwardly moving fuel feederblock, thus imposing undesirable, and sometimes damaging, stress in theStoker mechanism and needless expenditure of power. AS the feeding offuel by the Stoker cannot be readily observed, it is necessary toagitate the fuel .in the hopper frequently, or substantiallycontinuously, to break up masses or agglomerations of fuel and ensure aproper and uniform 'discharge of fuel from the hopper. Variousmechanical devices for this purpose have been proposed but for onereason or another these have not proved entirely satisfactory and, inconsequence, the usual method of agitation is hand poking by means of apoker introduced at the top of the hopper. In a continuously operatingplant of any considerable size this necessitates the Services of atleast one man per Working shift, that is, at least three men per 24-hourday. The resulting labour cost largely offsets the theoretical costsaving of mechanical stoking as compared with manual stoking.

The present invention provides power operated mechanical means forautomatically and effectively agitating fuel in a Stoker hopper inSuchwise that agglomerations of fuel in the hopper, whether introducedas such or due to packing of fuel in the hopper, are broken up andauniform discharge of fuel ensured; the Said means operating also toprevent passage from the hopper of fuel agglomerations or lumps so largeas to be caught between the edge of the hopper mouth and the fuel feederblock.

Broadly speaking, the invention consists in an agitator platereciprocable up and down in close proximity to the inner surfaces of aninclined wall of a Stoker hopper, Said plate having projecting therefrominto the hopper a series of tines; and driving'connection between saidplate and any suitable moving part of the Stoker.

In greater detail, the invention consists in the features andcombinations of features herein disclosed, together with all suchmodifications thereof and substitutions of equivalents therefore as areWithin the scope of the appended claims.

In the accompanying drawings which illustrate that embodiment of theinvention now preferred but to the details of whi-ch and to theparticular form of Stoker shown, the invention is not limited:

Fig. l is an elevation of the front of a conventional Stoker,illustrating the application of the invention thereto;

Fig. 2 is a vertical, longitudinal, sectional view of the Stoker, on theline 2-2 of Fig. l, illustrating the invention and its application to aStoker;

Fig. 3 is a vertical, transverse, sectional View of the Stoker, on theline 3 3 of Fig. 2, still further illustrating the invention and itsapplication to a Stoker;

Fig. 4 is a fragmentary sectional view, on an enlarged Scale, at theline 4--4 of Fig. 3, showing a detail of the agitator mounting;

Fig. 5 is an elevation, on an enlarged scale, of the tip of one of theagitator tines; and

Fig. 6 is a diagram illustrating the arrangement of the tips of lthetines.

Referring more particularly to the drawings, 11 designates the feedhopper of a conventional mechanical Stoker having a rearwardly anddownwardly inclined front wall 12, downwardly converging side walls 13and a rear wall 14. The lower edges lof the walls define a dischargeopening 15 leading to a fuel measuring chamber 16 formed by the sidewalls of the Stoker body, the sliding bottom 17 and the feeder block 18which is fixed to the front end of the sli-ding bottom. The slidingbottom and the feeder block thereon are reciprocated forwardly andrearwardly by a cross-head 19, `or equivalent, of form suitable to themotive power of the stoker. In the upper part of the hopper, a shield 20is provided, having front and side walls substantially paralleling theadjacent hopper walls and spaced inwardly therefrom to dene a pokingslot 21 at the front and Sides of the hopper.

An agitator plate.22 is slidably mounted within the hopper,substantially parallel with one of the inclined walls thereof,preferably the front wall 12, by means of parallel guides 23 xed to theinner surface of the hopper wall and extending substantially from top tobottom thereof. AS shown in Fig. 4, each guide comprises a spacer Strip24 to project between the hopper wall and an edge portion of the plate22 for elimination of friction between them; a filler strip 25 slightlythicker than the edge portion of the agitator plate and locatedoutwardly of the plate; and a cover strip 26 overlying the edge portionof the plate and retaining the same in proper relation to the hopperwall. To minimize entrance of grit into the guides, the inner or rearsurface of the agitator plate may be provided with projecting flanges 27engaging the cover strips so as to locate the contacting surfa-ces ofthe plate and strips above the main surface of the plate. The width ofthe agitator plate is preferably approximately the same as the width ofthevhopper discharge opening 15 but may be as much more as less as isdesired. The length of the plate 22 is preferably Such that it mayextend from the bottom of the hopper approximately half way to the topthereof, but may be morev or less. The lower edge portion 28 of theagitator plate iS bevelled on its rear surface to reduce resistance toplate movement 'downwardfy' between 'the hopper Wall and fuel in thehopper.

Any suitable means is provided `to `transmit power to the agitator plate'to reciprocate 'the same.` Preferably, this means is a 'movementtransmitting Lconnection between a moving part ofthe Stoker and the*pla-te and is adapted to `move the plate in synchronism with movementsof the feeder block.` In kstolcers of the vgeneral type illustrated, inwhich the feeder block is reciprocated by a `cross-head, it is 'mostconvenient to connect the movement transmitting means ofthe plate to thesto'ker crosshead, but it willbe understood (the invention is not thuslimited as :the connection may be 'to some different type of Stokerelement, such as a rotating shaft and through the intermediary of acrank, cam or eccentric. Obviously the plate may be powered by meansentirely separate from the Stoker.

p A plate reciprocating means suitable for the `type of Stokerillustrated comprises a transverse rock shaft 29 mounted atapproximately the level of 'the upper edge of the hopper wall, andoutwardly thereof, bymeans of bearings 30 fixed to the outer surface ofthe hopper wall. 1Arms31 are each fixed at one end to said shaft, towardthe ends thereof, and` project away from the hopper. These arms31arepivotally connected to the upper ends of links 3'2, the lower ends ofwhich are pivo'tally connected to the cross-head 19,` or equivalentreciprocating element of the stokenby means of studs 33 rigidly mountedin the cross-head. The yarms 31 are formed with a plurality yofapertures 34 for the pivotal connection of the `links 32 at any one of`a plurality of points in the lengths of the armsso that the extent ofoscillation of the arms and the shaft may be varied. An arm 35 is fixedto the shaft 29 in the vertical plane of the longitudinal axis `of ,theagitator plate and projects a short distance into the hopper. The freeend of this arm iS pivotally connected to the upper end of a link 36,the lower end of which is pivotally connected to the upper edge of theagitator plate. The link 36 is provided with a series of apertures 37for pivotal connection to the plate whereby the length ofthe `linkbetween the arm 35 and the plate 22 may be varied to adjust the plateupwardly or downwardly` in the hopper. Thearm 35 may be fixed to theshaft 29 by means of a tapered shear pin 38 passing through both the armand the shaft and threaded at its smaller end to co-operate with a nut39 Seating against the arm, whereby the pin may be retained in place andmay be tightened to take up wear. The arms 31 may be `fixed to the shaftin the same manner as the arm 35', or in any other manner desired. Itwill be seen that the arms ,31 and35 and the shaft connecting themconstitute a lever fulcrurned intermediate its ends and having one armconnected tothe agitator plate and the other arm connected to an`actuating means, the shaft being,` primarily, merely the pivotalmounting of the lever.

The agitator plate 22 carries a plurality of tines 40 rigidly mountedthereon and projecting into the hopper at an upward inclination. Thesetines are preferably arranged `in vertical rows, as shown in Fig. 3, andincrease in length fromltop toibottom ofthe rows so that each` lowertine `projects inwardly of the hopper beyond the tine next yabove it, asshown in Fig. 2. ln the outermost rows,` alternate` `tines may `standapproximately normal to the plate while the remaining alternate tinesare directed outwardly, or laterally, as shown inFig. 3, so that, whilethe roots of the` tines are in a single row at each side-of the plate,thetips of the tines are in two laterally spaced rows.` The plate `andtines may be regarded as constituting a rake andthe inclination of thetines as aforesaid increases the reach of the rake beyond the width ofthe plate. The tips of all tines lie substantially in a single planeinclined with respect to the plane of the plate 22 and nearer horizontalthan the plane of the plate. The inclination `of the plate; and thelengths of the tines are 4 so related that as the plate is moved up anddown in its plane, the tip o'f each tine 'traces a path 'different 'fromthat traced by the tip of any other tine. The tips of the tines arewedge shaped, as shown in Fig. 5, and the apex .edges 41 of alternatetines in 'a 'row are inclined oppositely to theapex edges of theremaining alternate tines of that row, and preferably oppositely to theapex `edges of the tines at the same level in adjacent rows, as shown inFig. 6. As will be seen, the tines project into the path of fuel moving`dow-n through the hopper to such an extent that the unobstructed paththrough the hopper is smaller than the hopper outlet.

In the upper part of the hopper, a` cover plate 42 extends from one tothe other of the guides 23 and from a level below the upper edge of theplate 22 upwardly into the space 21 between the shield -and the hopperwall and prevents material in the hopper from contacting the upper edgeof the agitator plate and the link 36 and arm 35 and also prevents thematerial from entering the guides above the `plate 22.

While the agitator of this invention has been illustrated as mounted onthe front wall of a hopper, it will be understood that, if desired, anagitator may be mounted on either or each of the side walls and that aplurality of similar agitators may be mounted, one on the front wall andone on either or each of the Side walls.

In the operation of a Stoker, the hopper is periodically filled withfuel, either `by hand or by descent through a chute. The fall of thefuel into the tapering hopper tends to cause the fuel to pack or wedgein the hopper and form a bridge or arch, especially in the lower part ofthe hopper, which must be broken to permit descent of the fuel formingSuch bridge and the fuel above it. In the lower part of the hopper, thematerial rests onthe plate 22 and the tines 40 are buried in thematerial. The movement of the plate operates to loosen an end of anybridge which may form, so that the bridge collapses. In addition, thetines 40, some of which will be buried in the bridge, will, by theirmovement, further break the bridge so that the fuel will descenduniformly `to the hopper outlet. It frequently happens that anagglomeration of fuel, larger than `the hopper outlet or larger than thecharging chamber 16 beneath the hopper, will enter the top of the hopperand become wedged part way down in the hopper with, to Some extent, thesame effect as a bridge of the fuel. Such lan agglomeration will besupported on the tips of the tines 40 so that some passage for fuelremains` between the agglomeration and the plate 22. As the agitatormoves up and down, the tines tear at the `surface of such anagglomeration along a multitude of paths lying in planes parallel to theplane of agitator movement and thus break up the agglomeration. As theplane containing the tips of the tines is inclined to the planes oftheir movement, the tines operate, during their upward movements, tolift the agglomcration so that it does not become wedged in the hopper;and also operate to rotate the agglomeration and, in time, tear atsubstantially the entire outer surface if the agglomeration shouldpersist for a suicient time. As the tines move up and down in contactwith the fuel, the lateral inclinations of the Surfaces of theirWedge-form tips produce lateral thrustings of the fuel which facilitateits downward movement and offset any tendency of tine movement to causea packing of fuel in the vertical direction. With tines of suitablelength, formed and arranged as described, agglomerations of fuel will,at the least, be reduced to such size that they will enter easily intothe charging chamber 16 of the Stoker and will not be caught between therear edge of the hopper outlet and the rear end of the feeder block 18during its rearward movement.

In the normal operation of a Stoker, with fuel in free flowing conditionin the hopper, there is considerable weight of fuel resting on thefeeder block during its rearward movement. According to this invention,the movement of the agitator is synchronized with the movement of thefeeder block, the agitator moving upwards during rearward movement ofthe feeder block and tending to lift the fuel in the hopper so as topartially relieve the downward pressure on the feeder block; and movingdownward during forward movement of the feeder block so as to urge fueldownwardly into the chamber 16.

While the invention has been `described in its application to amechanical stoker, it Will be obvious that its use is not thus limitedand that it may -be applied to facilitating movement through a hopper,of comminuted or granular material other than fuel.

Having thus ldescribed my invention, I claim:

l. A material agitator for hoppers comprising an agitator plate of awidth approximating the width of the hopper outlet, means for mountingsaid plate on the inner surface of an inclined wall of a hopper foredgewise sliding movement up and down in constant close proximity to andparallelism with said wall, .tines arranged in a plurality ofhorizontally spaced vertical rows projecting from said plate into thehopper for agitating material in the central portion of the hopper, andmeans for moving said plate upwardly and downwardly.

2. A device according to claim l in which the tines are wedge-shaped attheir free ends and the apex edges of the tine ends are inclined in thetransverse direction f the plate.

3. A material agitator for hoppers comprising an agitator plate, meansfor mounting said plate on the inner surface of an inclined wall of ahopper for edgewise sliding movement up and down in close proximity toand parallelism with said wall, tines projecting from said plate intothe hopper for agitating material in the hopper, and means for movingsaid plate upwardly and downwardly including a rock shaft to traversesaid inclined hopper wall adjacent and externally of the upper edge ofthe wall, means for mounting said rock shaft on the hopper, a

lever fixed at one end to said shaft, a link pivoted atv one end to saidlever and adapted to be connected at its other end to a powering elementfor movement in its longitudinal direction, a second lever fixed at oneend to said shaft and adapted to project into a hopper, and a linkconnecting said second lever and said plate.

4. A device of the class described comprising, in oombination, a hopperhaving an inclined wall, and an outlet, and an agitator plate mounted onthe inner surface of said hopper wall for sliding movement upwardly anddownwardly in a plane parallel with the hopper Wall, tines spacedvertically of said plate and also transversely thereof through adistance approximating the width of the hopper outlet and projectingfrom said plate into the hopper means to prevent material in the hopperfrom entering between the plate and the adjacent hopper wall, and meansfor moving said plate upwardly and downwardly.

5. A device according to claim 4 in which the free ends of some at leastof the tines are disposed at a distance from the opposite wall of thehopper which is materially less than the distance between said walls atthe outlet of the hopper whereby said tines overhang the outlet of thehopper to a material extent at all times.

6. A device according to claim 4 in which the tines are arranged invertical rows, the lengths of the tines increasing from the upper end ofeach row to the lower end thereof and the tips of the tines lying in aplane inclined more nearly to horizontal than the inclination of theplate whereby upon movement of the plate the tip of each tine will tracea path different from the path traced by the tip of any other tine.

7. A material agitator for a hopper comprising a plate, means formounting said plate on a hopper wall in an inclined position, means formoving said plate up and down in the plane of its inclination, tines xedto said plate to project into the central part of a hopper and incliningupwardly toward their free ends, said tines being disposed .at differentelevations and each lower tine being longer than the tine next above it,the lengths of the tines being such that the tips thereof occupy acommon plane inclined more nearly to horizontal than the plane of theplate.

8. A device according to claim 7 in which the tines are arranged in atleast three vertical rows and in the two outermost rows each alternatetine is laterally inclined away from the other outermost row while theremaining alternate tines of said rows stand approximately normal to theplate.

9. A device according to claim 7 in which the tips of the tines arewedge-shaped, the apex edges of the wedgeshaped tips being laterallyinclined.

10. A material agitator for hoppers comprising an agitator plate; meansfor mounting said plate on the inner side of an inclined hopper wall foredgewise sliding movement up and down in slightly spaced relation to andparallelism with said wall, comprising continuous guide members for theside edges of said plate and a stationary cover plate for the upperportion of said agitator plate to prevent entry of material from thehopper into the space between the agitator plate and the hopper wall;tines projecting from said plate into the hopper for agitating materialtherein; and means for moving said agitator plate upwardly anddownwardly.

1l. A device of the class described comprising the combination with ahopper having an inclined wall and a reciprocating material-feedingelement at the outlet of the hopper; of an agitator plate mounted on theinner surface of said inclined hopper wall for sliding movement upwardlyand downwardly; continuous guide members for the side edges of saidplate fixed to the hopper wall; a cover plate for said agitator platefixed to the hopper wall and extending from a level below the upper edgeof the agitator plate to substantially the upper edge of the inclinedhopper wall, said guide members and cover plate serving to excludematerial in the hopper from the space between the agitator plate and thehopper wall; tines projecting from said agitator plate into the hopper;and means for moving said agitator plate upwardly and downwardly.

12. In a stoker hopper, an agitator slidably related to a wall of thehopper for movement upwardly and downwardly, comprising a plurality oftines projecting into the hopper and located at a plurality of pointsspaced in the height and width of the hopper, said tines being arrangedto support an agglomeration of material in the hopper above the saidhopper wall and being of lengths suflicient to support an agglomerationof material at such distance from said hopper wall as to permit passageof unagglomerated material between the agglomeration and the hopper wallat substantially a normal rate Iof flow of material through the hopper;and means to move said agitator upwardly and downwardly.

13. In a stoker hopper, an agitator slidably related to a wall of thehopper for movement upwardly and downwardly, comprising a plurality oftines arranged at a plurality of points spaced in the height and widthof the hopper and projecting toward an opposite wall of the hopper, thelengths of some at least of said tines being such that the agitator willsupport an agglomeration of material too large to pass freely throughthe hopper outlet and at such distance from the hopper outlet as toleave the same unobstructed for passage of unagglomerated material atsubstantially a normal rate of ow of such material through the hopper;and means for moving said agitator upwardly and downwardly.

References Cited in the le of thisk patent UNITED STATES PATENTS1,472,280 Ousdahl Oct. 30, 1923 1,958,641 Roberts May 15, 1934 2,204,097Montgomery June 11, 1940

